In recent years, unprecedented huge changes in natural ecology in China are brought by woodland damage, river pollution, atmospheric pollution, etc., and the sharply reducing of lake wetland and the frequent climatic disasters, seismological and geological disasters prevent the people from doing nothing for ecological deterioration and slow nonfeasance. It is urgent to gradually reduce the damage to nature caused by people till the damage is stopped, and meanwhile, to restore the ecological environment.
Soil erosion indicates the damage to the covering of soil and the water washout to the bare soil which are caused by the soil utilization of human, especially, unreasonable development and management for soil and water resources, wherein the loss amount is more than the amount of the soil developed from parent material; the soil loss is formed by parent material loss resulted from surface soil loss and subsoil loss, and finally exposes the rock. Soil erosion is divided into three types: water erosion, gravitational erosion and wind erosion. Soil erosion is quite harmful, mainly at the following aspects: 1: causing productivity of land to decrease and even lose; 2: silting rivers, lakes and reservoirs; 3: polluting water quality and influencing ecological balance; 4: forming disasters, such as, debris flow, and the like, and seriously threatening the life safety of people.
According to the statistics of the Ministry of Water Resources in recent years, the soil erosion area of land in China reaches 3,570,000 km2, the total lost soil amount per year is about 5 billion tons, the lost cultivated land is about 666.6666667 km2, and the economic loss caused by soil erosion per year in China is about 2.6% of GDP. Therefore, if no forceful effective measure is taken by China for containing the soil erosion, the desertification and stony desertification of the mountainous area which is 70% of the national territorial area will be aggravated, and not only the sustainable development of economic society is restricted but also the ecological safety, food safety, flood control safety and even the national security of China will be seriously threatened.
Thus, how to effectively treat the soil erosion in the restoration for the ecological environment becomes the problem in sore need of solution in China at present. The ecological management for the soil erosion mainly adopts the method of planting vegetation on the surface of the bare rock-soil, so that the root system of the plants is utilized to fix the rock-soil, prevent rain wash and strong breeze from taking a large amount of soil and maintain the soil moisture.
When the vegetation is planted on the bare rock-soil and block slag piles during the process of treating the soil erosion, a large amount of gaps exist between the rock-soil and slag piles on the slope, so that humus soil which is at least 50 cm thick is firstly covered on the bare rock-soil as cover soil, and then the plants are planted on the cover soil, and the watering at regular intervals performed so as to ensure the survival rate of the plants; after the plants survive, the rock-soil will be fixed by the root system of the plants, so that the purpose of preventing the soil erosion is further achieved.
But, resulted from the restrictions of geographical factors, climatic factors, and the like, the traditional method for treating soil erosion is not applicable to the high and steep, abandoned slag piles at high elevation with large temperature difference in xerothermic drought valley, because the gradient of the slopes in these areas is large, the natural environment is poor, the areas are located remote and a large amount of humus soil is difficult to obtain from the surrounding of the treated slope as the cover soil source. If the soil which is originally barren and covered with vegetation on the surrounding of the slope is selected as the cover soil, new soil erosion will be resulted from excavating the massif in large scale for acquiring a large amount of cover soil, and the consequence of treating the present soil erosion by destroying the soil and water ecology in the other places is getting more kicks than halfpence.
On the other hand, the gradient of the slope is large (e.g. 25-60 degrees), so that even sufficient cover soil is found, the cover soil in at least 50 cm covering thickness is still difficult to attach to the slope under gravity action, and besides, the surface of the cover soil is loosening, major dry wind appears throughout the year and the rainfall is rare at high elevation with large temperature in xerothermic drought valley, so that the cover soil is easily peeled off and blown away before the vegetation is formed, thus, the conventional conservation of water and soil is not applicable to the high and steep, abandoned slag piles at high elevation with large temperature difference in xerothermic drought valley.
Besides, at the end of the 20th century, the development of the developed economies in the world is slowed down and the economy continues to worsen, so that our country, China, which relies heavily on export, investment and consumption, had to increase the investment portion and stimulate consumption so as to promote the economy. The investment contribution of the foundation engineering constructions, such as, hydropower construction, expressway, railway, under the condition of develop-the-west strategy is maximal. Moreover, for the expressway and high speed railway at tens of thousands of kilometers and thousands of large and medium hydropower station construction and large-scale excavation works, it is difficult to find enough site and ideal position for stacking the abandoned slag piles. Thus, stacking along the river and the slope becomes the helpless choice. Large-scale stacking for the abandoned slag piles firstly destroys the vegetation in these areas once again and further deteriorates the local ecological environment, and moreover, on the surface of the abandoned slag piles, the soil texture of the abandoned slag piles is loosening and the rock-soil in the abandoned slag piles is easy to run off under the effect of rain washing, so that the soil erosion and the ecological deterioration are further intensified.
These abandoned slag piles slopes are at high gradient and mostly locate in xerothermic drought western mountainous areas at high elevation with large temperature difference, therefore, the conventional water and soil conservation method is not applicable to treating the soil erosion of these abandoned slag piles.
Thus, a water and soil conservation method adapting to the high and steep, abandoned slag piles at high elevation with large temperature difference in xerothermic drought valley is desiderated at present.